1. Field of the Invention
The present invention relates to a liquid composition for ink jet printing, an ink set for ink jet printing, an ink jet recording method, and an ink jet recording apparatus.
2. Description of the Related Art
Ink jet systems for ejecting ink from an ink ejection port formed of a nozzle, a slit or a porous film have been used in many printers due to their being small-sized and inexpensive. Of these ink jet systems, a piezo ink jet system for ejecting ink by utilizing the deformation of a piezoelectric unit and a thermal ink jet system for ejecting ink by utilizing the boiling phenomenon of an ink by way of thermal energy are excellent in a high resolution and a high-speed printing property.
At present, increased speed and enhancement of picture quality on plain paper are taken as one of the important objective of an ink jet printer. In order to attaining this objectives, there has been proposed an image forming method of adhering a liquid containing a compound having a cationic group onto a recording medium and then adhering an ink containing an anion dye immediately after the liquid has permeated into the recording medium and is thus present in the medium, and has left the surface of the medium, thereby forming an amage (see U.S. Pat. No. 2,667,401, for example). In this method, in some cases in which the time required for drying of an ink is shortened, the density of an image is insufficient. In some cases in which printing is carried out with a small amount of drops, moreover, the long term ejecting property is insufficient.
In order to obtain a high-speed drying property, a high optical density and enhancement of picture quality, moreover, there has been proposed a color ink set characterized by a black ink containing water and a water-soluble solvent, a drying time on a piece of plain paper being equal to or less than five seconds, a color ink containing a coloring agent, water, a water-soluble solvent and a flocculant for flocculating the components of the black ink, and the time required for permeation in the plain paper being equal to or less than five seconds (for example, see JP-A No. 2001-294788). In some cases in which this system is used and a pigment is used for the coloring agent of a color ink, there is excellent optical density, blur and intercolor blur, but long-term storage stability is insufficient due to a flocculant. An electrolyte or a polyvalent metallic salt is usually used for the flocculant, and there is also a problem in that their effect as the flocculant are excessively great.
In order to improve jetting property of an inkjet sustem, moreover, there has been proposed an ink containing a nitrogen-containing five-membered ring keto acid such as pyrrolidone carboxylic acid or a salt thereof (see JP-A No. 63-265681; U.S. Pat. No. 2,711,888 and JP-A No. 2000-109735, for example). This system utilizes the effect of a moisturizing property provided by the nitrogen-containing five-membered ring keto acid salt and has an objective of improving the jetting property. In some cases in which a liquid containing the nitrogen-containing five-membered ring keto acid is used together with a liquid containing a coloring material as in the invention, however, it is impossible to achieve compatibility of picture quality and long-term storage stability.
As described above, with conventional methods, it is impossible to simultaneously have satisfactory optical density, blur, intercolor blur, drying time, and long-term storage stability.
Accordingly, the present invention has been made in view of the above circumstances and provides an ink set for ink jet printing, an ink jet recording method and an ink jet recording apparatus which are excellent in optical density, blur, intercolor blur, drying time, and long-term storage stability.
Further, the invention provides a liquid composition for ink jet printing to be used therein.